- PROCESS FOR THE HYDROGENATION OF AROMATIC COMPOUNDS
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The present invention focuses on a process for the hydrogenation of aromatic or heteroaromatic compounds and in particular on the ring hydrogenation of compounds having the formula (I). Aromatic amino acids and amino alcohols can be successfully ring-hydrogenated using a platinum-rhodium mixed catalyst. The products can be used inter alia as mimetics in bioactive peptide active ingredients.
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Page/Page column 12
(2008/06/13)
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- Stereoselective Aldol Reaction with Chiral Secondary Acetamides
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The deprotonated acetamides 4a - c and 5a - c are added to prochiral carbonyl compounds.The influence of the solvent, of the reaction temperature, and of the enolate gegenion on the ratio of the isomeric products 8/9, 18/19, and 26/27, respectively, are studied.The highest degree of diastereoselectivity are observed, when the titanium enolate of the acetamide 4a or the threefold deprotonated N-acetyl-α-phenylglycinol (5a) is used.The diastereomers 18a - d, formed in excess in the addition of 5a to aldehydes, are isolated in pure from by a single recrystallization, and afford the enantiomerically pure β-hydroxy carboxylic acids 3a - d.Thereby, the chiral auxiliary, α-phenylglycinol (14), is recovered.
- Devant, Ralf,Braun, Manfred
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p. 2191 - 2207
(2007/10/02)
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- Chiral (β-Aminoalkyl)phosphines. Highly Efficient Phosphine Ligands for Catalytic Asymmetric Grignard Cross-Coupling
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New chiral (β-aminoalkyl)phosphines, RCH(NMe2)CH2PPh2 , were prepared by starting with optically active amino acids.The phosphines were used as ligands for nickel-catalyzed asymmetric cross-coupling of 1-arylethyl Grignard reagents (ArMeCHMgCl) with vinyl bromide.Coupling products of over 70percent enantiomeric excess (ee) were obtained in the reaction with the ligand Phephos, Valphos, Ilephos, PhGlyphos, ChGlyphos, or t-Leuphos.A mechanism involving complexation of the magnesium atom in the Grignard reagent with the amino group on the (β-aminoalkyl)phosphine ligand is proposed to account for the high stereoselectivity.The asymmetric cross-coupling was applied to the synthesis of optically active 2-arylpropionic acids.
- Hayashi, Tamio,Konishi, Mitsuo,Fukushima, Motoo,Kanehira, Koichi,Hioki, Takeshi,Kumada, Makoto
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p. 2195 - 2202
(2007/10/02)
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- Synthesis of analogues of N (2 chloroethyl) N' trans 4 methylcyclohexyl) N nitrosourea for evaluation as anticancer agents
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The superior activity of N (2 chloroethyl) N' (trans 4 methylcyclohexyl) N nitrosourea (MeCCNU) against advanced murine Lewis lung carcinoma in comparisons with the cis form and other nitrosoureas prompted the synthesis of a number of MeCCNU analogues, including several cis trans pairs. The methyl group was replaced by a variety of substituents (CO2H, CH2CO2H, CO2Me, CH2OAc, CH2Cl, OMe); the trans 3 methylcyclohexyl, cis 2 methyl 1,3 dithian 5 yl, cis and trans 2 methyl 1,3 dithian 5 yl tetraoxide, and 1 methylhexyl (open chain) analogues were also prepared. Preliminary tests against murine leukemia L1210 revealed therapeutic indices (ED50/LD10) ranging from 0.26 to 0.79; all but 3 analogues effected 50% cure rates at nontoxic doses, the open chain analogue being one of the least active. In terms of therapeutic index, diequatorial (trans 4) isomers were, with one exception, as active as or, in 4 of the 8 examples, somewhat more active than the corresponding axial equatorial (cis 4) isomers. In this series, 4 of the 5 2-fluoroethyl analogues prepared were clearly inferior to the corresponding 2 chloroethyl analogues.
- Johnston,McCaleb,Clayton,Frye,Krauth,Montgomery
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p. 279 - 290
(2007/10/04)
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